1. Field of the Invention
The present invention relates to an image processing apparatus and an image processing method for converting a specific image in an input image into a pattern image.
2. Related Background Art
In a conventional image processing apparatus such as a facsimile apparatus for transferring image information, an original image is read by a photoelectric conversion element such as an image sensor, and is converted into a binary time-serial electrical signal. At this time, only the density of the original image is detected, and colors are not identified. For this reason, in a reproduced image, although a black portion of the original image is reproduced, colored figures or tables are reproduced in black and white, and the original image cannot be faithfully reproduced. For this reason, a halftone reproduction method such as a dither method, an error diffusion method, or the like is adopted to reproduce a halftone image. However, when density differences in units of colors are small, or gray is used, it is very different to express differences in colors. Although a copying machine, which reproduces an image by means of a multi-value output (i.e., plural bits per pixel per color), can express density differences, when density differences in units of colors are small, or gray is used, it is also very different to express differences in colors. For this reason, in the field of, e.g., copying machines, image processing for recognizing colors, converting information of each respective color into predetermined patterns corresponding to the various colors, and outputting the converted patterns has been proposed.
However, with an MH or MR method as an encoding method as in the GIII standards, a halftone image based on the dither method or the error diffusion method undesirably has a huge information volume, which causes increases in communication time and communication cost. In addition, it is difficult to reproduce differences in colors, as described above. When color pattern conversion is performed at a resolution of 400 dpi, if the pattern is converted to the resolutions of 8 pel and 3.85 line/mm of the GIII standards in a facsimile transmission, the pattern is painted solid, and as a result, reproducibility is impaired. Furthermore, when an arrangement for generating only a binary pattern is adopted in correspondence with a facsimile image, the performance of the multi-value pattern copying machine cannot be utilized.